Coal-Fired Power Plant, and Method for Operating Coal-Fired Power Plant

Abstract

A coal-fired power plant having a control unit including a first flow rate control valve for regulating a water flow rate of a water feed bypass system, a second flow rate control valve installed in an extraction pipe for extracting steam from a steam turbine, a first temperature sensor on a downstream side of a heat recovery device, and a second temperature sensor on a downstream side of a heat exchanger and the control unit regulates opening of the first and second flow rate control valves on the basis of an exhaust gas temperature detected by the first temperature sensor and a feed water temperature detected by the second temperature sensor. Accordingly, even when a recovery heat quantity of the heat recovery device installed on a gas duct is changed due to deterioration with age of a boiler, a reduction in plant reliability and plant efficiency can be suppressed.

1 . A coal-fired power plant comprising:
 an exhaust gas discharge system for flowing exhaust gas discharged from a boiler flow,   a steam supply system for driving a steam turbine by steam generated by the boiler and feeding the steam to a condenser after driving the steam turbine, and   a water feed system for feeding water condensed by the condenser to the boiler, wherein:   the water feed system includes a feed water heater having a heat exchanger for heating the water by steam extracted from the steam turbine, and   a water feed bypass system is provided at an upstream side of the heat exchanger to exchange heat between the exhaust gas flowing through the exhaust gas discharge system and the water of the water feed system by a heat recovery device which is installed in the water feed bypass system, characterized in that:   a control unit including a first flow rate control valve for regulating a water flow rate flowing in the water feed bypass system, a second flow rate control valve installed in an extraction pipe for extracting steam from the steam turbine,   a first temperature sensor installed on a downstream side of the heat recovery device, and a second temperature sensor installed on a downstream side of the heat exchanger, wherein the control unit regulates openings of the first and second flow rate control valves on the basis of an exhaust gas temperature detected by the first temperature sensor and a feed water temperature detected by the second temperature sensor.   
     
     
         2 . The coal-fired power plant according to  claim 1 , wherein:
 the feed water heater comprises a plurality of heat exchangers and   the second temperature sensor is installed on the downstream side of the respective heat exchangers.   
     
     
         3 . The coal-fired power plant according to  claim 1 , wherein:
 the first flow rate control valve controls an opening thereof on the basis of an entrance gas temperature of an electric dust collector installed on the downstream side of the heat recovery device.   
     
     
         4 . The coal-fired power plant according to  claim 1 , wherein:
 the second flow rate control valve controls an opening thereof on the basis of the feed water temperature discharged from the heat exchanger.   
     
     
         5 . The coal-fired power plant according to  claim 1 , wherein
 a plurality of the heat exchangers and a plurality of the heat recovery devices are arranged as a pair, a water feed bypass system for branching on the upstream side of each of the heat exchangers is provided, and   the control unit regulates a flow rate of feed water to be fed to the heat recovery device positioned on a high-temperature side of the water feed system from among the plurality of heat recovery devices so as to increase the flow rate thereof.   
     
     
         6 . An operating method for a coal-fired power plant comprising:
 an exhaust gas discharge system for flowing exhaust gas discharged from a boiler flow,   a steam supply system for driving a steam turbine by steam generated by the boiler and feeding the steam to a condenser after driving the steam turbine, and   a water feed system for feeding water condensed by the condenser to the boiler, wherein:   the water feed system includes a feed water heater having a heat exchanger for heating the water by steam extracted from the steam turbine, and   a water feed bypass system is provided at an upstream side of the heat exchanger to exchange heat between the exhaust gas flowing through the exhaust gas discharge system and the water of the water feed system by a heat recovery device which is installed in the water feed bypass system, comprising a step of:   regulating a water flow rate flowing in the water feed bypass system and an extraction rate for extracting steam from the steam turbine on the basis of a exhaust gas temperature on a downstream side of the heat recovery device and a feed water temperature on a downstream side of the heat exchanger.